For the 139 patients who were followed from 2 to 7 years in the Collaborative Branch Vein Occlusion Study, the proposed study will investigate 1) statistical analysis of retinal vascular photographic characteristics related to prognosis, laser treatment adequacy, and edema mechanisms, and 2) new statistical methods for the analysis of visual acuity. This group of 139 patients has now been closed out from the Collaborative Study with the major goal for this group achieved and published. Through this work, it has been established that laser photocoagulation is beneficial in lessening visual loss from macular edema that is secondary to retinal branch vein occlusion, for those patients who meet the eligibility requirements of the study and who were treated with the argon laser according to the study protocol. This proposal will review the photographic documentation of retinal characteristics that may be expected to offer a more accurate prognosis to the individual patient. Such features will include anatomical extent and severity of edema, presence of foveal hemorrhage, intact peri-foveal capillaries, etc. New statistical methodologies will be explored to examine 1) the time course of visual acuity change, 2) the stability of visual acuity, and 3) approaches to combining the expression of both vision gain and loss. The analyses of prognostic features (risk factors), through an examination of these abnormalities, may have relevance to other retinal vascular diseases, such as diabetic retinopathy.